1. Field of the Invention
The present invention relates to a method of producing a light-reflective film. More specifically, the present invention relates to a method of producing a light-reflective film that includes a light-reflecting layer in which a cholesteric liquid crystal phase has been fixed.
2. Description of the Related Art
In recent years, as interest in the environment and energy has been heightened, the need for industrial products relating to energy saving has been increased. As one of the industrial products, a heat-shielding product for window glass of houses or automobiles, that is, a light-reflective film for glass that has an effect of reducing a thermal load caused by sunlight is in demand.
As eco-glass having a high insulating and heat-shielding property, a multi-layered glass coated with a special metallic film that blocks radiant heat, which is called Low-E pair glass, is widely used. The special metallic film can be prepared by laminating a plurality of layers by, for example, a vacuum film-forming method. However, the productivity of the vacuum process is low, and the production cost thereof is high. Moreover, in many cases, the light-reflective film for glass is required to transmit light of a wavelength other than the target reflection wavelength due to the use thereof. For example, for automobile windows, the light-reflective film is required to have a property of reflecting infrared light but reliably transmitting visible light, from the viewpoint of safety. In addition, the light-reflective film is required to accomplish a high transparency (haze reduction or the like). However, when the metallic film is used, the high transparency is not necessarily satisfied. Moreover, other improvements are required for the light-reflective film, from the viewpoint of a radio wave-transmitting property or the like.
In this respect, an infrared light-reflecting film obtained by laminating a layer in which a curable cholesteric liquid crystal phase has been fixed (hereinafter, also referred to as a “cholesteric liquid crystal layer” in some cases) on a support has been suggested (for example, see JP2010-286643A). As a method of laminating a plurality of cholesteric liquid crystal layers, JP2010-286643A discloses a method of drying coating films containing cholesteric liquid crystal materials, aligning the coating films by heating, followed by ultraviolet curing, and laminating the coating films layer by layer. However, JP2010-286643A does not disclose a step of finally winding up the light-reflective film in which the cholesteric liquid crystal layers have been laminated and does not disclose the characteristics of the light-reflective film wound up. Moreover, JP2010-286643A does not disclose continuously laminating the cholesteric liquid crystal layers layer by layer while transporting the support when the coating film containing the cholesteric liquid crystal materials is dried, aligned by heating, and cured with ultraviolet. JP2010-286643A also does not disclose a production method including winding up once the coating film containing the cholesteric liquid crystal materials at a point of time when one layer of the coating film has been layered, when the cholesteric liquid crystal layers are continuously laminated.